One of the features of this invention is to provide an improved heat exchanger that is particularly adapted for cooling lubricating oil in an engine in which the coolant chambers for the two heat exchange fluids are formed by stacked spaced plates in a casing or tank with spacer means for defining the extent of the two sets of chambers with the result that the heat exchanger structure is simple in design, inexpensive to make and readily serviced when requied.
Another feature of the invention is to provide such a heat exchanger with improved valve means that is automatically operated by the high viscosity of one of the fluids such as lubricating oil at a relatively low temperature where cooling is not required so as to bypass much of the cooling capacity of the exchanger.
The most pertinent prior art of which applicant is aware is his own U.S. Pat. No. 3,743,011 which is also a heat exchanger and specifically an oil cooler made up of stacked plates and which also discloses two embodiments of pressure controlled bypass of one of the fluids such as oil. The present invention differs from this in providing certain structural advantages which are disclosed and claimed in the present application.